The present invention relates to novel tricyclic compounds which strongly antagonize an action of thromboxane A.sub.2 (hereafter referred to as TXA.sub.2).
It is hitherto known that TXA.sub.2 strongly aggregates platelets and is a percent vasoconstrictor [cf. Arachidonic Acid Cascade and Drugs, edited by Shozo Yamamoto, Gendai Iryo Publishing Co., Ltd. (1958)]. Further TXA.sub.2 is a powerful vasoconstrictor against bronchus and bronchial smooth muscle Therefore, TXA.sub.2 is considered to take part in pathological conditions over a wide range. The following diseases can be exemplified.